"tony thomas" wrote in message
news:Oh5Nd.51517$eT5.37379@attbi_s51...
I don't know the exact number for that particular year/engine. However, it
should be between 120 and 130.

If you get much below 120 I would be suspicious. Pick up a light scope
(small light on a flexible line) so you can see inside the cylinder. You
can see if there are any scratches in the cylinder walls around the intake
and exhaust ports.

Most problems occure on the intake port side due to water and/or poor
oiling.

Most problems occure on the exhaust side and or top of piston due to low
octane fuel/lean condition.

Thanks, Tony. Yes, often (especially in a salt water used engine) you can
get a blockage from salt in the powerhead and that can cause over heating
and a virtual "frying" of the cylinder(s). It can happen even before the
powerhead in the copper water tube coming from the pump. I had a Merc. 90 HP
2-stroke with the water tube collapsed from salt at the base of the
powerhead and that restricted the water flow by about 50%, effectively
destroying that powerhead by over heating. I did rebuild it myself and I got
it going again for about $1500.00 in parts and machining for the complete
engine and gear case. Basically, it was a total rebuild of about 18 hours.
It runs just fine now. In fact, it's got a great deal of "snap" :-) And much
cheaper than a new unit. It's on the back of a 22' Boston Whaler now and 55
MPH is not a problem.

--
Tony
my boats and cars at http://t.thomas.home.mchsi.com
wrote in message
oups.com...
"Jim and Becky" wrote in message
...

OK I agree, but if all six cylinders have 70-80 psi isn't there a
problem?

It could very well be. Was that the reading? Check your service manual.
The specs will be in there.

I'm thinking the 120-140 psi range is what I'm looking for based of
something I read long ago.
Hence my latest question.

Keep in mind, also, you are only allowed a certain percentage variation
between cylinders and that varies from make of engine and model etc..
Again, get a service manual. Or call the dealership. Get the correct
specs. If you don't know, you will be in trouble. A compression test
will detect the most basic defects and wear. On some engines, having a
high compression reading could mean having carbon build up, but that
mostly happens on lower RPM engines like Tecumseh or B&S engines. If
it's a EFI that should not be happening mind you. Still, get the specs,
look for variation and low compression. Anything that is out of spec,
run away from - unless you can get it dirt cheap.